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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 29 April 2011 by dana1981

In 1988, Hansen et al. published a global temperature projection which thus far has turned out to be quite accurate, and yet which numerous "skeptics" have widely criticized and misrepresented. As brought to our attention by Skeptical Science reader Jimbo, noted "skeptic" climate scientist Richard Lindzen gave a talk at MIT in 1989 which we can use to compare to Hansen's projections and see who has been closer to reality over the past two decades. Although to our knowledge Lindzen has never made any specific global temperature projections, he did make some statements in this talk which we can use to extrapolate what his temperature predictions might have looked like.

For example, Hansen and colleagues at NASA Goddard Institute for Space Studies (GISS) began compiling a global surface temperature record (GISTEMP) in 1981. As of 1988–1989, their temperature record showed that the average surface temperature had risen approximately 0.5 to 0.7°C since 1880, when the record begins. Lindzen, however, disputed the accuracy of GISTEMP:

"The trouble is that the earlier data suggest that one is starting at what probably was an anomalous minimum near 1880. The entire record would more likely be saying that the rise is 0.1 degree plus or minus 0.3 degree....I would say, and I don't think I'm going out on a very big limb, that the data as we have it does not support a warming. Whether it contradicts it is a matter of taste"

It turns out that Lindzen's first statement here was incorrect. According to the slightly longer temperature record of the Hadley Centre, 1880 was closer to a local maximum than a minimum. But more importantly, he is claiming here that the average global surface temperature trend between 1880 and 1989 is approximately 0.1°C. Lindzen proceeds to effectively assert that any greenhouse gas warming signal is swamped out by the noise of natural internal variability.

"I personally feel that the likelihood over the next century of greenhouse warming reaching magnitudes comparable to natural variability seems small"

As we recently discussed, natural variability rarely results in more than 0.2 to 0.3°C warming on decadal timescales, so Lindzen is clearly predicting a very small amount of greenhouse warming over the next century. Using these quotes, I reconstructed what I think are two reasonable approximations of global temperature projections based on Lindzen's belief of the small warming effects of greenhouse gases. I want to be explicit that these projections are my interpretation of Lindzen's comments, not Lindzen's own projections.

In both reconstructions, I used the 1880 GISTEMP temperature anomaly (-0.3°C) as the baseline and added some random noise with an amplitude consistent with internal variability (approximately 0.4°C). In the first reconstruction, I then simply added in a linear trend of approximately 0.1°C warming per century.

In the second Lindzen reconstruction, I first calculated, assuming Lindzen's purported 0.1°C warming between 1880 and 1989 were accurate and was caused by CO2 (since the net non-CO2 forcing has been approximately zero), what the climate sensitivity would be, using the following formula and the CO2 levels in 1989 (353 ppm) and pre-industrial (280 ppm):

For a temperature change of 0.1°C, this results in a climate sensitivity parameter (λ) of 0.08 Kelvin per Watts per square meter, or 0.3°C for a doubling of atmospheric CO2. For comparison, the IPCC most likely climate sensitivity value is ten times larger, at 3°C for doubled CO2.

I then used this sensitivity in the same formula above with the annual CO2 levels to add the annual CO2 temperature change to the 1880 baseline plus random noise for Lindzen reconstruction #2.

Alongside these reconstructions I also plotted Hansen et al. (1988) Scenarios A, B, and C. As discussed by NASA GISS's Gavin Schmidt, Scenario B was the closest to the actual radiative forcing changes since 1998, but was approximately 10% too high in this regard. Thus I also created an "adjusted" Scenario B to reflect what Hansen's data would have looked like had he correctly projected the greenhouse gas increase.

As you can see, Hansen's Scenario B is not far from reality, with a warming trend since 1984 (0.26°C per decade) approximately 30% too high (compared to our average GISTEMP trend of 0.20°C per decade), and the adjusted Scenario B even closer, with a warming trend just 17% higher than observed.

Our reconstructions of Lindzen's projections, on the other hand, increasingly diverge from reality. His warming trend of approximately 0.01°C to 0.02°C per decade is 90 to 95% too low. This is further illustrated in the figure below, which isolates the adjusted Scenario B, our second Lindzen reconstruction, and the GISTEMP average (we have also added this figure to the high resolution climate graphics resource page).

Additionally, Dr. Hansen's 1988 climate model was a bit more sensitive to greenhouse gas changes than the models used by climate scientists today, with a sensitivity of 4.2°C for a doubling of CO2. We can further adjust his Scenario B to reflect the IPCC climate sensitivity of 3°C to determine what today's climate model projections would have looked like in 1988.

As you can see, the projection matches up very well with the observed temperature increase. This supports the IPCC most likely climate sensitivity value of 3°C for doubled CO2.

This analysis demonstrates that Hansen has a record of highly accurate climate projections over the past two decades, while Lindzen has a record of inaccuracy. Indeed, Lindzen continues to argue for low climate sensitivity to this day (not quite as low as 0.3°C, but he continues to argue it's below 1°C for doubled CO2 [i.e. Lindzen and Choi 2009]).

Given all the heat "skeptics" have directed towards Hansen for his projections' slight overestimate of the subsequent warming, one can only wonder what they must think about the massive underestimate of this warming based on Lindzen's 1989 comments.

Hansen has a great deal to say about aerosols as a negative forcing in his book Storms of My Grandchildren (Pgs. 98-99). Without aerosols, net forcing is about 3 watts (W m2). Aerosols have a forcing of 0 to -3 watts, with a most likely value of -1 watt, thus reducing net forcing to 2 watts. Thus, aerosol cooling might be masking about one-third the greenhouse forcing.

But if aerosol forcing is -2 watts, reducing the net forcing to 1 watt, then aerosols have been masking most of the warming. Further cleaning up the air would then result in a doubling of the net climate forcing from what we've been observing.

Hence his labeling of our GHG/aerosol emissions as a "Faustian Bargain".

@97 to 99, I am aware that Scenario C emissions have been significantly lower than real-world emissions since 2000. Therefore, Scenario C temperature projections should be below observed temperatures but this is obviously not the case. Real-world temperatures track Scenario C very closely from 1958 to present. Coincidence? Perhaps.

Dana addressed this problem with his 2.7°C sensitivity Scenario D and achieved good results. However, this change is not "minor". It has resulted in the 2019 temperature projections plummeting from 1.57°C/1.10°C in Hansen (1988) to 0.69°C in Dana (2011).

This is a dramatic drop of either 0.88°C or 0.41°C depending on which version of Hansen 1988 you prefer.

"Therefore, Scenario C temperature projections should be below observed temperatures but this is obviously not the case. "

For crying out loud Angus, the reason for this has been explained to you ad nauseum. One really has to wonder if you are being deliberately obtuse on this point, or repeatedly repeating a falsehood in the hopes that is becomes true. Scenario C is relatively close to observations (for now at least) because of because of two errors: too low emissions run used as input into a climate model with too high a sensitivity (~4.2 C for doubling CO2).

Instead of accepting the fact that Lindzen's hypothesis is woefully wrong and cannot explain the observed warming (the point of the post), you seem to be doing everything you can to convince yourself that equilibrium sensitivity is not near +3 C for doubling CO2.

Two quotes for you to think about:

"Beware those who deride predictive science in its entirety, for they are also making a prediction: that we have nothing to worry about. And above all, do not shoot the messenger, for this is the coward’s way out of openly and honestly confronting the problem" [Dr. Kerry Emmanuel]

"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence." [John Adams]

Regarding your statement that I am trying to convince myself that "equilibrium sensitivity in not near +3°C." This is patently untrue. I stated @81 and @103 that Dana's Scenario D with a sensitivity of 2.7°C gives good results.

I fully understand your "ad nauseum" reasoning that two errors may be cancelling each other out to give the correct answers in Scenario C. This is why I suggested Hansen's aerosol strategy to correct Scenario B.

I am willing to wait for a few years (but not ad infinitum) to determine if real-world temperatures will start to follow real-world emissions again or if they will continue to bump along the commitment trajectory. The date of 2015 suggested by Hansen (2006) seems as good a time as any to determine which trajectory real-world emissions are following.

You may wish to consider Sir Arthur Conan Doyle, "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."

Thinking some more about the possibility that we are following scenario C due to an aerosol boom, I note that land temperatures have continued to rise in the last 10 years, and the gap between land and ocean temps has also increased.

This suggests that even over the last 5 or so years external forcing is still firmly in warming mode, and that ocean variability has led to the current short term pause.

And it would appear that Co2 forcing is high enough to completely offset any aerosol cooling due to any impact by China, and the solar minimum.

Well, I read the links to see if Charlie A was right in this thread or not. This paragraph seems to be the relevant:

Nor, he said, was the temperature data collected in a very systematic and uniform way prior to 1880, so comparisons often begin with temperatures around 1880. "The trouble is that the earlier data suggest that one is starting at what probably was an anomalous minimum near 1880. The entire record would more likely be saying that the rise is 0.1 degree plus or minus 0.3 degree."

If I read that correctly, Lindzen is claiming that the reason the ITR shows warming from 1880 is that 1880 was a local minima. 'The entire record' seems to refer to a fictitious but accurate temperature record going back rather further. His suggestion is therefore that the early 19th C temperatures were rather warmer, and that warming relative to the long term average is therefore rather smaller.

My reading may be wrong, but it does look to me as though Charlie has a point: The reconstruction of Lindzen does not reflect what Lindzen is actually saying. Lindzen's claims may be confused and bizarre, they certainly contradict multiple sources of data, but I don't think he is claiming what the graph shows.

He referred to MIT Professor Reginald Newell's work that suggests that between the 19th century and the present there appears to be no change in ocean surface temperatures. Moreover, the record for the 48 contiguous states shows no evidence for warming over the past century.

"As far as the data goes, I would argue that we really don't have the basis for saying it's a half degree plus or minus 0.2. That is false use of science. What we have is data that says that maybe it occurs, but it's within the noise."

Lindzen is clearly saying, here, that there has been no warming to speak of this century, and so his own baseline starts well below the actual warming we've seen, which is where Dana put it. It's Lindzen's prediction and Lindzen's interpretation of the observations that is being used.

That Lindzen was so wildly in denial back in 1989 is his own fault and no one else's.

Now some may consider this unfair, because Lindzen is being hit with a double whammy in his prediction, by both choosing a starting point far below reality (because he refused to believe there even was any warming) as well as choosing a climate sensitivity that precludes virtually any warming at all and in fact constrains everything within a very narrow range.

So what Charlie A is really asking is that we excuse Lindzen's refusal in 1989 to accept the temperature record, and so now to let him hindcast himself back into reality... and then let his bad prediction go on from there, from a more accurate starting point (but one that was not a part of his very wrong 1989 view of the climate).

As an aside, a discussion of Linzen's presentation from 1989 is a true Gish Gallop of unbelievable denial tripe. He was already laying the groundwork (a true climate pioneer!) of the denial arguments we see today. It's fun to see them in their early, less polished form. And it's overall pretty comical to read now, in 2011, knowing where things have gone, and what has and has not come to fruition since then.

Oh yes, I see your point. (And I think you can also see how Charlie and I reached our conclusion?)

Given the Lindzen's counterfactual picture of the temperature record, I guess Dana's line is as good as any. Sadly that's not a very satisfying criteria. I suppose presenting an ensemble of possible lines with Lindzen's gradient on the whole record might be more realistic, but that's ugly and arguably misleading too (and wouldn't fit on the graph for the new article). OK, I give up.